Does your child have an official ASD diagnosis? Generally SSI for a young child is much easier than an adult, and often you do not need an attorney. I will say however the more documentation you have the better off you are. I would not go by a school diagnosis though if that is all you have, I would go to a real doctor, either a Neurologist or a Psychologist.

Get all records every year at the end of the school year. Hopefully the school is documenting any problem behaviors or difficulties your child has. Also keep all IEP records as well. For our son, walking into Social Security with 2 5 inch thick files of papers as documentational proof of his disability went a long way without having to say much on my part. Of course I made sure to have the main papers I needed such as the diagnosis sheet on the top for easy access. If they needed any other documentation to prove his disability, I welcomed them to feel free to search through the documentation and find what they needed. The worker declined the invite.

another note is the schools do NOT give diagnosis. They find children eligible under a disability category, but it is not a medical or legal diagnosis for anyone outside of the school system. A child who has a medical diagnosis of autism, may not qualify for services in a school, but that doesn't mean they don't have autism. The reverse is also true, a school may find a child needs services and fits under the autism category, but doesn't have a medical diagnosis (or has a medical diagnosis of some other diability).

We did all our psych, behavioral, OT, autism specialis and speech assessment through her school and had her reg. doctor fill out paperwork as well showing his diagnosis. That way when we filed for her SSI we didn't have any problems. So more paperwork you have the better.

social services will have a form they send to the school for his teacher to fill out and will request a copy of his most recent IEP and possibly the eligibility summary.